Zellner D, Zellner G E, Keller F
Division of Nephrology, Medical Department, University of Ulm, Ulm, Germany.
Comput Methods Programs Biomed. 2001 Jun;65(3):183-90. doi: 10.1016/s0169-2607(00)00119-x.
The assessment of sample size in clinical trials comparing means requires a variance estimate of the main efficacy variable. If no reliable information about the variance of the key response is available at the beginning of a clinical trial, the use of data from the first 'few' patients entered in the trial ('internal pilot') may be appropriate to estimate the variance and thus to recalculate the required sample size. A SAS macro that implements the EM algorithm for carrying out and simulating such interim power evaluations without unblinding the treatment status is presented.
在比较均值的临床试验中评估样本量需要对主要疗效变量进行方差估计。如果在临床试验开始时没有关于关键反应方差的可靠信息，那么使用试验中最初纳入的“少数”患者的数据（“内部预试验”）来估计方差，进而重新计算所需样本量可能是合适的。本文介绍了一个SAS宏，该宏实现了期望最大化（EM）算法，用于在不揭示治疗状态的情况下进行和模拟此类中期效能评估。
